Abstract: This is an essay in the field of metallurgical engineering. Thermodynamics of the reaction, hydrochloric acid leaching for waste ceria-based rare earth polishing powder, was studied in this work.The influences on the leaching rate of the waste polishing powder was respectively considered including hydrochloric acid concentration and leaching temperature in the experiment. The result of the Gibbs free energy of leaching reaction and leaching experiment showed, thermodynamics theoretical analysis was consistent with experiment date for CeO₂ and La₂O₃. CeO₂ could not be immersed in dissolution, and La₂O₃ was easy to get leached. However, the experiment result was quite opposite of theoretical thermodynamics calculation for Al₂O₃. The Gibbs free energy of leaching reaction for Al₂O₃ were always a positive value, and Al₂O₃ from the waste polishing powder couldn’t be immersed by hydrochloric acid, but experiment result indicated that the Al₂O₃ leaching rate can be stabilized above 91%. Amorphous forms Al₂O₃ had high reactive activity in the waste, but the thermodynamic parameter of inert Al₂O₃ crystal structure (corundum) was adopted in the Gibbs free energy calculation.